Javascript base 10 and 62 conversion to each other

function string10to62(number) {
  var chars = '0123456789abcdefghigklmnopqrstuvwxyzABCDEFGHIGKLMNOPQRSTUVWXYZ'.split(''),
    radix = chars.length,
    qutient = +number,
    arr = [];
  do {
    mod = qutient % radix;
    qutient = (qutient - mod) / radix;
    arr.unshift(chars[mod]);
  } while (qutient);
  return arr.join('');
}

function string62to10(number_code) {
  var chars = '0123456789abcdefghigklmnopqrstuvwxyzABCDEFGHIGKLMNOPQRSTUVWXYZ',
    radix = chars.length,
    number_code = String(number_code),
    len = number_code.length,
    i = 0,
    origin_number = 0;
  while (i < len) {
    origin_number += Math.pow(radix, i++) * chars.indexOf(number_code.charAt(len - i) || 0);
  }
  return origin_number;
}